Common sense holds that your brain sees an object, and then recognizes it. But a new study shows that the reality may be the reverse. Your expectations shape what you see.
There is an area of every person's brain, the fusiform face area, that is in charge of recognizing faces. When a complete stranger comes up to you in the street, greets you like an old friend, and engages you in conversation, either your fusiform face area is letting you down or theirs is letting them down. Or you're being grifted. In any case, hang on to your wallet.
It was thought that the brain processed stimuli the way large companies process orders. Neurons at the bottom of a chain of command bring in data and pass it up the line. The higher level neurons take the raw data and either match it up appropriate responses, or if more work is necessary, add a little more data and pass it higher. The brain responded to external sources of data.
A new study indicates that the brain actually processes stimuli the way large companies implement policies: from the top down. High level brain cells form an expectation of certain data, and hand it down to the lower neurons. The neurons process it dutifully, and only hand it back up if there is some kind of conflict. The response to things are, at least to a certain extent, internally driven.
In an experiment, people hooked up to an fMRI were asked to look at a series of pictures. The pictures were either of faces or of houses. If the responses of the brain were entirely externally driven, the fusiform face area would not respond to the houses the same way it did to the faces. And often, it did not. When the subjects were put in situations where they expected to see a face, however, the FFA responded to houses almost the same way it did to faces. When someone expects to see something, their brains will behave as if they did see it until they get a strong signal to behave otherwise.